A communication system is operative to transmit information between two or more locations and includes, at a minimum, a transmitter and a receiver interconnected by a communication channel. A radio communication system is a communication system in which the communication channel comprises a radio frequency channel wherein the radio frequency channel is defined by a range of frequencies of the communication spectrum.
The transmitter which forms a portion of the radio communication system includes circuitry for converting the information into a form suitable for transmission thereof upon a radio frequency channel. Such circuitry includes modulation circuitry which performs a process referred to as modulation. In such a process, the information which is to be transmitted is impressed upon a radio frequency electromagnetic wave, commonly referred to as a carrier signal. The resultant signal is commonly referred to as a modulated signal. Such resultant signal is also referred to as a communication signal as the modulated signal includes the information which is to be communicated between the transmitter and the receiver.
Radio communication systems are advantageous in that no physical interconnection is required between the transmitter and the receiver; once the information signal is modulated to form a modulated signal, the modulated signal may be transmitted over large distances.
A two-way radio communication system is a radio communication system, similar to the radio communication system above-described, but which further permits both transmission of information to a location, and transmission of information from that location. Each location of such a two-way radio communication system contains both a transmitter and a receiver. The transmitter and the receiver positioned at a single location typically comprise a unit referred to as a radio transceiver or, more simply, a transceiver.
A cellular communication system is a type of two-way radio communication system in which communication is permitted with a radio transceiver positioned at any location within a geographic area encompassed by the cellular communication system.
A cellular communication system is created by positioning a plurality of fixed-site radio transceivers, referred to as base stations, at spaced-apart locations throughout the geographic area. The base stations are connected to a conventional, wireline, telephonic network. Each base station has associated therewith a portion of the geographic area located proximate to each of such base stations. Such portions are referred to as cells. The plurality of cells, each defined by corresponding ones of the base stations of the plurality of base stations, together define the coverage area of the cellular communication system. A radio transceiver, referred to in a cellular communication system as a radiotelephone, positioned at any location within the coverage area of the cellular communication system is able to communicate with a user of the conventional wireline, telephonic network by way of a base station. Communication signals generated by the radiotelephone are transmitted to a base station, and then, by way of the conventional, wireline, telephonic network to a desired wireline location to effectuate thereby telephonic communication therewith. Telephonic communication may also be effectuated with the radiotelephone upon initiation at the wireline location.
One type of radiotelephone construction is commonly referred to as a portable radiotelephone as such construction of radiotelephone is of dimensions permitting carriage thereof by a user. A portable power supply, typically comprised of a battery pack having one or more battery cells, is affixed to, to be carried with, the portable radiotelephone. Such portable power supply is suitably connected to the radiotelephone to provide power to the radiotelephone during operation thereof.
Because a battery stores only a finite amount of energy, operation of the portable radiotelephone is limited by the energy storage capacity of the portable power supply. Powering of the portable radiotelephone by the portable power supply depletes the power supply of stored energy. Once the portable power supply becomes discharged, replacement of such supply is necessitated to permit continued operation of the radiotelephone.
While the energy storage capacity of the portable power supply may be increased, such increase in capacity typically only may be effectuated with a concomitant increase in the size and weight of the portable power supply. Such increase in the energy storage capacity of the portable power supply may only, therefore, be effectuated by decreasing the portability of the assembly comprised of the portable radiotelephone and portable power supply carried therewith.
Accordingly, efforts have been made to increase the period of operability of the portable radiotelephone when powered by a single, portable power supply by reducing the amounts of power required to operate the portable radiotelephone. By increasing the efficiency of operation of the circuitry of the radiotelephone, an increase in the period of operability of the radiotelephone may be effectuated even without an increase in the energy storage capacity of the power supply used to provide power to the radiotelephone to permit operation thereof.
Circuitry which permits operation of the radiotelephone while requiring lesser amounts of power for operation of such radiotelephone will further increase the period of operability thereof.